Thriving On Low Carbonhttp://blog.energysmiths.com/
How I'm thinking about our house, transportation, food and waste, to minimize environmental impact, while improving quality of life and having fun.en-US2017-04-01T10:06:22-04:00

Observations on variations in energy usagehttp://blog.energysmiths.com/2017/04/observations-on-variations-in-energy-usage.html
The morning of the first day of each month is when I read the meters and download another month's worth of circuit data from the SiteSage monitor. I have 39 months of data now. There are some items so consistent that I could move the current transformers to other unmonitored...<p>The morning of the first day of each month is when I read the meters and download another month&#39;s worth of circuit data from the SiteSage monitor. I have 39 months of data now. There are some items so consistent that I could move the current transformers to other unmonitored circuits, for example the clothes washer - 0.4 kWh/month, month after month. We apparently aren&#39;t substantially dirtier season to season. Then there are the predictable seasonally variable loads - the refrigerator and freezer use more energy in the summer (low 40s each per month) and less in winter (high 20s). Similarly, the heat pump water uses more in the winter when the basement is cooler (low 60Fs) and less in summer as it warms up, while our usage of hot water is remarkably consistent at 14 gallons daily.</p>
<p>Once I gather the data each month, one of the first things I look at is the net energy flow - did we need to import energy from the grid, or did we have a surplus of generation and therefore exported energy? This can vary substantially. Let&#39;s look at March, the month just past.Here are the net kWh for each of the four months of March 2014 - 2017:</p>
<p>March 2014 - 29 kWh imported</p>
<p>March 2015 - 48 kWh exported</p>
<p>March 2016 - 216 kWh exported</p>
<p>March 2017 - 53 kWh exported</p>
<p>Quite a variation - what&#39;s happening? Well, the big variations are in the weather - how cold and how cloudy was each month? In the table below, all values are kWh except for heating degree days base 65 (HDD65) and the ratio of energy used by the heat pump to the HDD65.</p>
<table style="height: 154px;" width="630">
<tbody>
<tr>
<td style="width: 68.7833px;">&#0160;</td>
<td style="width: 62.1px;">Used</td>
<td style="width: 84.5333px;">Generated</td>
<td style="width: 61.4667px;">Net</td>
<td style="width: 64.3667px;">Heat pump</td>
<td style="width: 67.1667px;">Used except heat pump</td>
<td style="width: 68.5833px;">HDD65</td>
<td style="width: 101px;">HP kWh/HDD65</td>
</tr>
<tr>
<td style="width: 68.7833px;">Mar-14</td>
<td style="width: 62.1px;">565</td>
<td style="width: 84.5333px;">536</td>
<td style="width: 61.4667px;">29</td>
<td style="width: 64.3667px;">343</td>
<td style="width: 67.1667px;">222</td>
<td style="width: 68.5833px;">1043</td>
<td style="width: 101px;">0.33</td>
</tr>
<tr>
<td style="width: 68.7833px;">Mar-15</td>
<td style="width: 62.1px;">446</td>
<td style="width: 84.5333px;">494</td>
<td style="width: 61.4667px;">-48</td>
<td style="width: 64.3667px;">247</td>
<td style="width: 67.1667px;">199</td>
<td style="width: 68.5833px;">1023</td>
<td style="width: 101px;">0.24</td>
</tr>
<tr>
<td style="width: 68.7833px;">Mar-16</td>
<td style="width: 62.1px;">358</td>
<td style="width: 84.5333px;">574</td>
<td style="width: 61.4667px;">-216</td>
<td style="width: 64.3667px;">150</td>
<td style="width: 67.1667px;">208</td>
<td style="width: 68.5833px;">789</td>
<td style="width: 101px;">0.19</td>
</tr>
<tr>
<td style="width: 68.7833px;">Mar-17</td>
<td style="width: 62.1px;">461</td>
<td style="width: 84.5333px;">514</td>
<td style="width: 61.4667px;">-53</td>
<td style="width: 64.3667px;">209</td>
<td style="width: 67.1667px;">252</td>
<td style="width: 68.5833px;">1013</td>
<td style="width: 101px;">0.21</td>
</tr>
</tbody>
</table>
<p>In March 2014, I was still working out the control settings on the heat pump which caused it to cycle to full speed then stop, so the high usage that month is primarily the heat pump. In March 2016, the weather was sunnier than normal, and much warmer - presto, a large net export of energy. Our usage in March 2015 and March 2017 was very similar, as was the solar generation, so the net export numbers were almost the same. The heat pump used less in 2017 for a similar amount of heating demand, and I&#39;m pretty sure this is partially accounted for by Jill building a few fires in the woodstove on cold evenings. Our usage of energy besides the heat pump was up in 2017 over 2015 - no one item stands out, but slightly more use of the range, lights and plug loads, HPWH, and ERV add up.</p>
<p>Over the long haul it tends to average out, but we don&#39;t draw too many conclusions from one year&#39;s worth of data!</p>Marc Rosenbaum2017-04-01T10:06:22-04:00Consumption and generation for 2016http://blog.energysmiths.com/2017/01/consumption-and-generation-for-2016.html
This year total usage here at the house is 3,808 kWh. Of that, 1,037 kWh went into the Fujitsu heat pump; 861 kWh went to the refrigerator and chest freezer; 598 kWh were used for water heating in the heat pump water heater; 176 kWh used in the range, and...<p>This year total usage here at the house is 3,808 kWh. Of that, 1,037 kWh went into the Fujitsu heat pump; 861 kWh went to the refrigerator and chest freezer; 598 kWh were used for water heating in the heat pump water heater; 176 kWh used in the range, and 164 kWh by the well pump (dry summer, lots of drip irrigation); lights and plug loads totaled 315 kWh. November and December were just a bit colder than the 5 year average, after a very warm winter last year.</p>
<p>The PV system generated 6,309 kWh, for a net export of 2,501 kWh. We really should be driving an electric car!</p>
<p>This winter I&#39;m re-doing experiments I did last winter, with (I hope) better set-ups. I&#39;m measuring the effectiveness of the Zehnder ComfoAir 200 ERV at recovering heat from the exhaust air and putting it into the supply air. And I&#39;m logging pressure difference between the basement and outdoors, as well as outdoor temperature, and attempting to find correlation with radon levels.</p>Marc Rosenbaum2017-01-02T10:55:03-05:00Deep Energy Retrofit Online Course starts Sept 12th!http://blog.energysmiths.com/2016/08/deep-energy-retrofit-online-course-starts-sept-12th.html
I'm teaching a 10 week in-depth course for professionals who are serious about transformative energy upgrades to residential and commercial buildings. We'll cover the pertinent building science, techniques for superinsulating foundations, walls, windows, and roofs, appropriate mechanical systems. There will be a weekly in-depth case study as well. Please join...<div class="entry-body">
<p>I&#39;m teaching a 10 week in-depth course for professionals who are serious about transformative energy upgrades to residential and commercial buildings. We&#39;ll cover the pertinent building science, techniques for superinsulating foundations, walls, windows, and roofs, appropriate mechanical systems. There will be a weekly in-depth case study as well. Please join us, and pass this on to anyone who might benefit. Here&#39;s the link:</p>
<p><a href="https://www.heatspring.com/courses/deep-energy-retrofits" target="_blank">Deep Energy Retrofits Online Course</a></p>
</div>Marc Rosenbaum2016-08-25T13:20:00-04:00Great video on a Deep Energy Retrofit to Net Positive Energyhttp://blog.energysmiths.com/2016/02/great-video-on-a-deep-energy-retrofit-to-net-positive-energy.html
My friend John Livermore is multi-talented, and enlisted his 17 year old daughter and his stepson as well to produce a tremendously clever and fun 10 minute video on how they transformed their 70s raised ranch from an energy hog to a net energy producer, shrinking their carbon footprint to...<p>My friend John Livermore is multi-talented, and enlisted his 17 year old daughter and his stepson as well to produce a tremendously clever and fun 10 minute video on how they transformed their 70s raised ranch from an energy hog to a net energy producer, shrinking their carbon footprint to a fraction of its initial size. Full disclosure: I was one of the participants.</p>
<p>Check it out <a href="http://www.healthyhomehealthyplanet.org/">here</a></p>Marc Rosenbaum2016-02-11T18:09:50-05:00Deep Energy Retrofits of Historic Buildingshttp://blog.energysmiths.com/2016/02/deep-energy-retrofits-of-historic-buildings.html
Here is a PDF of my talk today at the RISD Architecture Dept. Tomorrow we look at the retrofit possibilities at their 50,000 ft2, 1848 building, the Bayard Ewing Building. Download Historic Buildings RISD 2016<p>Here is a PDF of my talk today at the RISD Architecture Dept. Tomorrow we look at the retrofit possibilities at their 50,000 ft2, 1848 building, the Bayard Ewing Building. <span class="asset asset-generic at-xid-6a014e86fffc67970d01b7c80fbf43970b img-responsive"><a href="http://thrivingonlowcarbon.typepad.com/files/historic-buildings-risd-2016.pdf">Download Historic Buildings RISD 2016</a></span></p>Marc Rosenbaum2016-02-01T15:28:37-05:00Deep Energy Retrofit Online Course starts Sept 14th!http://blog.energysmiths.com/2015/08/deep-energy-retrofit-online-course-starts-sept-14th.html
I'm teaching a 10 week in-depth course for professionals who are serious about transformative energy upgrades to residential and commercial buildings. We'll cover the pertinent building science, techniques for superinsulating foundations, walls, windows, and roofs, appropriate mechanical systems. There will be a weekly in-depth case study as well. Please join...<p>I&#39;m teaching a 10 week in-depth course for professionals who are serious about transformative energy upgrades to residential and commercial buildings. We&#39;ll cover the pertinent building science, techniques for superinsulating foundations, walls, windows, and roofs, appropriate mechanical systems. There will be a weekly in-depth case study as well. Please join us, and pass this on to anyone who might benefit. Here&#39;s the link:</p>
<p><a href="https://www.heatspring.com/courses/deep-energy-retrofits" target="_blank">Deep Energy Retrofits Online Course</a></p>Marc Rosenbaum2015-08-26T18:17:14-04:00Retrofits vs. Reductionshttp://blog.energysmiths.com/2015/08/retrofits-vs-reductions.html
I’m excited because I’ve been putting together a new online course on Deep Energy Retrofits (DER). More so than the course I teach on Zero Net Energy Homes, it’s focused on the multiple approaches and techniques for taking the diverse building stock we have and transforming it – not just...<p><a class="asset-img-link" href="http://thrivingonlowcarbon.typepad.com/.a/6a014e86fffc67970d01b7c7c4dd12970b-pi" style="display: inline;"><img alt="P1020393" border="0" class="asset asset-image at-xid-6a014e86fffc67970d01b7c7c4dd12970b image-full img-responsive" src="http://thrivingonlowcarbon.typepad.com/.a/6a014e86fffc67970d01b7c7c4dd12970b-800wi" title="P1020393" /></a></p>
<p>I’m excited because I’ve been putting together a new online course on Deep Energy Retrofits (DER). More so than the course I teach on Zero Net Energy Homes, it’s focused on the multiple approaches and techniques for taking the diverse building stock we have and transforming it – not just from the standpoint of energy use, but also upgrading comfort, health and safety, and durability – because so much of our building stock is plagued with deficiencies. Retrofits fix the issues with the building asset and saving energy almost ends up as a desirable byproduct. There are so many different buildings and conditions, and therefore solutions, so the DER course is based on case studies and we show many approaches people have chosen to implement.</p>
<p>&#0160;If energy saving is the principal goal, it’s important to look carefully at the choices the occupants make. Energy in buildings goes to more than heating and cooling, which are the main loads that retrofits target. Over forty percent of primary energy in US homes goes to non-thermal loads. Once we superinsulate a house in New England, energy for heating, once the largest load by a comfortable margin, may become the smallest load amongst heating, domestic hot water (DHW), and plug loads/lighting/appliance loads (PLA). To get to truly low energy performance then requires focus on DHW and PLA.</p>
<p>&#0160;With motivated occupants, it’s possible to get deep energy <em>reductions</em> without DERs. &#0160;People can do a moderate weatherization on a house, then install a point source heater such as a single zone minisplit heat pump to keep the most-used part of the house comfortable. The rest of the house runs cooler and the main heating system stays off until the outdoor conditions get severe. Lots of savings have been demonstrated in this approach. Couple that with LED lighting replacement in high use fixtures; great low flow showerheads like the Delta H2OKinetic; a horizontal axis washer; and depending on the household size, perhaps a heat pump water heater. Replace the dryer with a drying rack and a clothesline. Make a concerted attempt to keep appliances and entertainment stuff off when not using it. Hunt down phantom loads.&#0160;</p>
<p>&#0160;Combine all of the above and the total outlay might be $10-20,000 and the energy saved might equal or even exceed what a second household might achieve that goes the whole enchilada and does a DER, if that second household is much less conscious of their DHW and PLA usage, and heats the whole retrofitted house to comfort temperatures. I definitely see DER households using a pretty wide range of energy per person. The climate doesn’t care <em>how</em> we each reduce our consumption, just that we do. Of course a motivated, conserving&#0160; household in a DER will have the lowest energy usage of all, but if a household is committed to reducing their carbon emissions, they needn’t spend six figures to get there. What the DER gets that the targeted weatherization, behavior-based deep energy reduction strategy may not is relief from the non-energy deficiencies – ice dams, pest infestations, water issues, mold, etc., and true comfort. The cost of remediating those defects shouldn’t have to be paid for solely by the energy savings that accrue.</p>
<p>&#0160;I live in a zero net energy DER after previously weatherizing a pretty good house and also reaching zero net energy. I like the second house a lot better, because of its superior comfort and air quality. But I spent a lot more money to get there, and the total energy performance isn’t much better, because DHW and PLA usage is pretty similar. The DER uses less energy for heating at an even 70F setpoint than the pretty good house used with some temperature setback and letting parts of the house get cooler. I hope to live in this retrofitted house for a long time, and it’s worth it to me to have spent what I did to get a house my wife and I are so pleased to inhabit. I’m just not fooling myself that I needed a DER to achieve deep energy reductions, if that was my only goal.</p>
<p>&#0160;To learn more about the transformative possibilities of Deep Energy retrofits, please join me starting September 14<sup>th</sup> in the ten week online course – check it out at <a href="https://www.heatspring.com/courses/deep-energy-retrofits" target="_blank" title="Deep Energy Retrofit online course"><span style="text-decoration: underline;">Deep Energy Retrofit online course</span></a></p>
<p>Photo courtesy Janice and Steve Kurkoski<span style="text-decoration: underline;"><br /></span></p>
<p>&#0160;</p>
<p>&#0160;</p>
<p>&#0160;</p>Marc Rosenbaum2015-08-26T18:11:06-04:00Reflections on Building Energy 2015http://blog.energysmiths.com/2015/03/reflections-on-building-energy-2015.html
For 36 years, my professional community has been the Northeast Sustainable Energy Association. This past week we gathered once again in Boston for the Building Energy Conference. It was one of the best ever. I go to Building Energy to get my mind twisted out of my ordinary fixed ideas...<p>For 36 years, my professional community has been the Northeast Sustainable Energy Association. This past week we gathered once again in Boston for the Building Energy Conference. It was one of the best ever. I go to Building Energy to get my mind twisted out of my ordinary fixed ideas and to learn new ways to think. This year was a bumper crop.</p>
<p>I took a half day workshop with Greg Norris, who is an expert in Life Cycle Assessment (LCA), which seeks to quantify the embodied energy, water, and other impacts in materials and products. He recently become Chief Scientist at the <a href="http://living-future.org/" target="_blank" title="ILFI">International Living Futures Institute</a>, whose first initiative is the Living Building Challenge,&#0160; but who are going beyond that to products and neighborhoods.</p>
<p>In this workshop on non-toxic materials was the most inspiring thing I heard at the entire conference -&#0160; the concept of handprinting. The premise is that everything we buy or consume has a footprint, and even a vegan bike-riding solar powered person dressed in second hand clothes has a footprint – there’s no such thing as a zero footprint. In other words, a footprint represents what we take. But we can act positively as well – a simple example is planting a tree – and those actions can use the same analytic tools in many cases to tally up the give as well as the take of our selves and organizations. Handprinting combined with footprinting leads to the concept of NetPositive, giving more than we take. I found it to be a liberating construct. One exciting aspect is that the definition of what constitutes a handprint vs. a reduced footprint is yet to be fully defined in relation to buildings. When we design and build a net zero building, is the baseline the code building, or is it no building? Big difference! Thanks to Greg for doing this work!</p>
<p><a href="http://www.chgeharvard.org/resource/building-netpositive-enterprises">http://www.chgeharvard.org/resource/building-netpositive-enterprises</a></p>
<p><a href="http://www.chgeharvard.org/topic/handprint-new-unit-measuring-impact">http://www.chgeharvard.org/topic/handprint-new-unit-measuring-impact</a></p>
<p>Footprinting and LCA were embedded into the conference. South Mountain Company has been footprinting our operations - office and shop and jobsite energy, employee transportation, materials transportation. The most obvious conclusion has been that employee transportation on the Island is the largest portion by far, and we&#39;ve recently re-aligned our benefits and incentives to promote higher efficiency transportation, chiefly electric vehicles. Byggmeister and SMC presented a session on our beginner&#39;s steps on this stuff, and Byggmeister&#39;s work focused beyond ours to include the embodied energy in the materials they put into place. We&#39;re starting a similar effort in analyzing a couple of the affordable houses we&#39;ve built. Detailed stuff, would make even a bookkeeper&#39;s brain trip out on overload!</p>
<p>Howard Brown of dMass and Mark Loeffler of Atelier 10 spoke about the dematerialization of our economy. Brown was a student of Buckminster Fuller and reminds us that people want benefits not products, and every effort to deliver the benefits with less mass gets closer to the proposition of <a href="http://www.amazon.com/Naked-Value-Resources-Innovation-Competition/dp/0985447400" target="_blank" title="Naked Value">naked value</a>, and has lower environmental impact. As Howard succinctly says, benefits are weightless. What was inspiring was the number of items they showed that last year were in development and this year were on the market. Brown emphasizes that it’s increasingly common that breakthroughs are being made by people without specialized training but rather a determination to find a better way to do something.</p>
<p>Examples of cool stuff:</p>
<p>- Piezoelectric tiles in high traffic areas like subway stations to generate electricity</p>
<p>- Ecovative adding to their base business of producing packing material&#0160; from ag waste and fungal mycelium to making structural biocomposites to replace materials like OSB</p>
<p><a href="http://www.ecovativedesign.com/products-and-applications/structural-biocomposites/">http://www.ecovativedesign.com/products-and-applications/structural-biocomposites/</a></p>
<p>- Concrete cloth – rolls of cloth impregnated with cement, dampen and it sets up</p>
<p>- Building-integrated wastewater hydropower in high rise buildings, and power from pressure reducing valves in pipelines</p>
<p>- Active ceramic anti-bacterial tiles - <a href="http://www.active-ceramic.com/antibacterial-tiles/">http://www.active-ceramic.com/antibacterial-tiles/</a></p>
<p>The closing forum had three old farts, I mean, friends and three young superstars each doing 20 slides in the pecha kucha technique. It was a rousing and inspiring finish to a great gathering – old guys John Abrams, Terry Brennan, and Chuck Silver, with the young-uns Stephanie Horowitz, Ace McArleton, and Declan Keefe showing us the way to the future.</p>
<p>I got to meet past and new students from my Zero Net Energy Homes Online Course, about to begin on Monday the 9th. And I saw hundreds of friends and colleagues, all gathered to vision a better future, and share wholeheartedly our collective experience on how to get there. If you missed BE this year, well, like the Sox, there&#39;s always next year.</p>Marc Rosenbaum2015-03-07T12:48:22-05:00Zero Net Energy Homes Course starts March 9thhttp://blog.energysmiths.com/2015/02/zero-net-energy-homes-course-starts-march-9th.html
3 weeks from now, NESEA and I will once again offer the Zero Net Energy Homes online course. Who do you know whose practice could really benefit from a more rigorous and quantitative understanding of building science, solar energy, superinsulated construction, ventilation, renewable energy, and low energy use mechanical systems?...<p><a class="asset-img-link" href="http://thrivingonlowcarbon.typepad.com/.a/6a014e86fffc67970d01b8d0d8617e970c-pi" style="display: inline;"><img alt="Rosenbaum, 2of10 - SW Ext After" border="0" class="asset asset-image at-xid-6a014e86fffc67970d01b8d0d8617e970c image-full img-responsive" src="http://thrivingonlowcarbon.typepad.com/.a/6a014e86fffc67970d01b8d0d8617e970c-800wi" title="Rosenbaum, 2of10 - SW Ext After" /></a><br />3 weeks from now, NESEA and I will once again offer the <a href="https://www.heatspring.com/courses/zero-net-energy-homes" target="_blank" title="ZNE Homes Online Course">Zero Net Energy Homes online course</a>. Who do you know whose practice could really benefit from a more rigorous and quantitative understanding of building science, solar energy, superinsulated construction, ventilation, renewable energy, and low energy use mechanical systems? It&#39;s a packed 10 weeks, and includes a bunch of Excel calculators so folks can do a simple heat loss; calculate frame assembly thermal bridges; estimate hot water energy requirements; calculate the solar gain through the glazing; and do a simple annual energy calculation in order to size the PV system. In the videos I cover energy, heat transfer, moisture, thermal bridges, superinsulated construction, ventilation and heating/cooling, DHW, solar thermal and solar electricity.</p>
<p><br />As a bonus, enrolling in the course includes a membership in NESEA!<br /><br />From participants:<br /><br />&#0160;“I would just like to take this moment of enthusiasm and express how terrific I think this course is.”<br /><br />Wayne (architect)<br /><br />&#0160;“These calculators are great. The ability to tweak a couple of factors and see the whole system impact is outstanding. I feel like these are great tools to &quot;nudge&quot; clients towards better performing buildings as we can attach dollar amounts to heat loss....”<br /><br />Bryan (design/builder)<br /><br />&#0160;“The quality of teaching in your course is amazing, every word choice, how clearly the ideas are outlined, the various calculators are incredible. I&#39;m only on week 2 and I can&#39;t believe how much I&#39;ve learned.”<br /><br />Lucy (homeowner doing a Deep Energy Retrofit)<br /><br />&#0160;“Both NESEA and Marc have given me a tremendous leg up in my work, shortening my learning curve by months if not years in some areas.”<br /><br />Newell (company president, timber framer, design/builder)</p>
<p>&quot;I really, really enjoyed the course, Marc! While my wife truly grew to resent the amount of time I spent on the computer every evening, the grief I suffered was worth it. It was a real treat to have such an experienced professional open their reserves of knowledge up to anybody keen enough to listen. Most courses in energy efficient construction and sustainable design are too fluffy and general; having some math and spreadsheets to really sink our teeth into was an absolute gift. Thank you very much for the wonderful generosity of your time and attentive responses. In a world where mentorship in the construction world is all but lost, it is a terrific thing you are doing to keep the future of the industry headed down the path that yourself and your colleagues have got us started on.&quot;</p>
<p>Burke (builder)</p>Marc Rosenbaum2015-02-17T17:54:15-05:00Minisplit heat pumps and blizzardshttp://blog.energysmiths.com/2015/02/minisplit-heat-pumps-and-blizzards.html
A blizzard (a severe snowstorm and sustained winds of over 35 mph) is a challenging weather condition for a minisplit heat pump. Recall how an air source heat pump works - the outdoor unit has a compressor and a fan that blows air across a coil with refrigerant. In heating...<p><a class="asset-img-link" href="http://thrivingonlowcarbon.typepad.com/.a/6a014e86fffc67970d01b7c74d7d1b970b-pi" style="display: inline;"><img alt="Photo 5" border="0" class="asset asset-image at-xid-6a014e86fffc67970d01b7c74d7d1b970b image-full img-responsive" src="http://thrivingonlowcarbon.typepad.com/.a/6a014e86fffc67970d01b7c74d7d1b970b-800wi" title="Photo 5" /></a><br />A blizzard (a severe snowstorm and sustained winds of over 35 mph) is a challenging weather condition for a minisplit heat pump. Recall how an air source heat pump works - the outdoor unit has a compressor and a fan that blows air across a coil with refrigerant. In heating mode, the coil is colder than the outdoor air. As air is drawn through the coil it gives up heat to the coil and leaves the other side colder. The more humid the air (and the warmer the air is, the more moisture it can hold), the more condensation occurring on the coil. At temperatures at or below freezing, that condensation may freeze on the coil, reducing air flow through the coil and heat transfer to the refrigerant. Heat pumps are designed to sense this type of condition, and periodically operate a defrost cycle, in which the heat pump reverses and uses some energy to melt the frost off the coils. Below is the Fujitsu condenser at House 5 with frost building up:</p>
<p><a class="asset-img-link" href="http://thrivingonlowcarbon.typepad.com/.a/6a014e86fffc67970d01b8d0d6dac9970c-pi" style="display: inline;"><img alt="P1060218" border="0" class="asset asset-image at-xid-6a014e86fffc67970d01b8d0d6dac9970c image-full img-responsive" src="http://thrivingonlowcarbon.typepad.com/.a/6a014e86fffc67970d01b8d0d6dac9970c-800wi" title="P1060218" /></a></p>
<p>Here&#39;s the same condenser after the defrost cycle:</p>
<p><a class="asset-img-link" href="http://thrivingonlowcarbon.typepad.com/.a/6a014e86fffc67970d01b8d0d6dafd970c-pi" style="display: inline;"><img alt="P1060220" border="0" class="asset asset-image at-xid-6a014e86fffc67970d01b8d0d6dafd970c image-full img-responsive" src="http://thrivingonlowcarbon.typepad.com/.a/6a014e86fffc67970d01b8d0d6dafd970c-800wi" title="P1060220" /></a></p>
<p>Here&#39;s a Daikin condenser that I <em>think</em> has a faulty defrost cycle (photo taken at a house at which South Mountain has installed a solar electric system) - the frost has built up considerably:</p>
<p><a class="asset-img-link" href="http://thrivingonlowcarbon.typepad.com/.a/6a014e86fffc67970d01b7c74d7fca970b-pi" style="display: inline;"><img alt="Minisplit condenser frost" border="0" class="asset asset-image at-xid-6a014e86fffc67970d01b7c74d7fca970b img-responsive" src="http://thrivingonlowcarbon.typepad.com/.a/6a014e86fffc67970d01b7c74d7fca970b-800wi" title="Minisplit condenser frost" /></a></p>
<p>So, the above photo excepted, this is under normal conditions, not a blizzard. Here&#39;s a screenshot of the power input to the Fujitsu at our house on January 26th as the temperatures rose and the blizzard began:</p>
<p><a class="asset-img-link" href="http://thrivingonlowcarbon.typepad.com/.a/6a014e86fffc67970d01b7c74d81d4970b-pi" style="display: inline;"><img alt="Defrost 15-01-26 blizzard" border="0" class="asset asset-image at-xid-6a014e86fffc67970d01b7c74d81d4970b image-full img-responsive" src="http://thrivingonlowcarbon.typepad.com/.a/6a014e86fffc67970d01b7c74d81d4970b-800wi" title="Defrost 15-01-26 blizzard" /></a></p>
<p>Through about 2 pm, the temperatures were in the mid-to-upper 20Fs, and the defrost cycles, marked by the dips in power draw, occurred roughly every 4 hours, lasted 4-5 minutes, and drew under 250W. Once the storm starts up, temperatures are right around freezing, and the fine snow is being whipsawed around by the strong winds, which can drive the snow into the coil, coating it and triggering the defrost cycle. The blizzard becomes a moisture delivery system. The defrost cycles are much more frequent, slightly over once per hour. And the duration rises to 15 minutes or so, with a power draw of 500W. Note also that after the defrost cycle the heat pump power draw jumps up to 900W or so, whereas before the storm it&#39;s running at 450W much of the time.&#0160; It appears that the firmware drives the heat pump up to the higher power draw for a certain amount of time after every defrost cycle, and when the cycles are frequent, it never drops down to the &quot;cruising&quot; power draw. So both efficiency and capacity are reduced, because the energy going into defrost isn&#39;t going into the house. You can tell when the defrost cycle occurs because the indoor fan shuts off, otherwise it would be blowing cold air.</p>
<p>The condenser needs clearance beneath it, because the melt from the defrost cycle is going to freeze once it drips down off the condenser, and in the worst case it freezes under the condenser and crushes the lowest row of the coil and the unit is ruined. So it makes sense to raise the condenser above snow line and keep it under an overhang or roof.</p>
<p>This all becomes more severe if the condenser is actually buried in snow. In the worst case, the heat pump shuts down, and we saw this at a couple of houses here. My own unit is up off the ground, and under a small roof, but the Jan 26-27 storm came from the northeast and still packed the gap between the house and condenser 40-50% full of snow. We&#39;re considering doing more wall mounted installations, getting them at least 2 feet off the ground, but architects don&#39;t want to see the condenser(s), so the inclination is to install them low to the ground and behind screening. But this usually makes them more vulnerable. Here&#39;s a neat wall mounted installation:</p>
<p><a class="asset-img-link" href="http://thrivingonlowcarbon.typepad.com/.a/6a014e86fffc67970d01bb07f1357b970d-pi" style="display: inline;"><img alt="Wall mounted minisplit heat pump Kulpa" border="0" class="asset asset-image at-xid-6a014e86fffc67970d01bb07f1357b970d image-full img-responsive" src="http://thrivingonlowcarbon.typepad.com/.a/6a014e86fffc67970d01bb07f1357b970d-800wi" title="Wall mounted minisplit heat pump Kulpa" /></a></p>
<p>We&#39;ve been pleased that these seem not to impart vibration to the house, the units must be very well-balanced.</p>
<p>Does this mean that houses heated by minisplit heat pumps, with no back-up heating system, are more vulnerable in bad storms than houses heated by modern fossil fuel burning equipment? Not necessarily - those have their own issues in the storms. Sealed combustion sidewall vents can be plugged by ice or wind-driven snow, and wind gusts can cause the pressure sensing switch to shut the units down. So modern heating systems in general are more twitchy in severe weather than the old atmospherically vented boiler venting into a interior masonry chimney, with a barometric damper. Do we want to go back to that? For a number of reasons, I&#39;d say no. Houses that need that big boiler or furnace are much more likely to freeze up when that unit goes down (say in a power outage) than a small superinsulated house with a minisplit. My sense is, get &#39;em up off the ground, and check them in a bad storm.</p>
<p>&#0160;</p>Marc Rosenbaum2015-02-15T12:37:09-05:00